Floating holder



J 1969 M. L. BENJAMIN ETAL 3,421,770

FLOATING HOLDER Filed Feb. 18, 1966 Sheet of 2 INVENTORS MILTON L.M/AM/N r 5' DAV/0 D. W KER ATTORNEYS M 1.. BENJAMIN ETAL 3,421,770

Jan. 14, 1969 FLOATING HOLDER Filed Feb. 18, 1966 Sheet '9 of2 INVENTORSI MILTON L. BENJAMIN DAV/D 0. WALKER ATTORNEYS United States PatentClaims ABSTRACT OF THE DISCLOSURE A floating holder in which the toolgripping bushing is mounted for limited radial movement to accommodatefor axial misalignment between the tool and a workpiece, and a springcentering mechanism for yieldably maintaining the bushing in axialalignment with the holder.

The present invention relates generally, as indicated, to a floatingholder and, more particularly, to a tool holder in which the tool ismounted for direct radial movement into axial alignment with a workpieceto be machined thereby.

Oftentimes when performing secondary machining operations on a workpiecesuch as reaming a bored or drilled hole, it is diflicult accurately toalign the reamer with the hole, whereby the hole may be reamedout-of-round. This is especially true in the case of turret latheshaving a plurality of tools such as drills, boring bars, reamers, andtaps mounted thereon for sequential axial feeding with respect to arotating workpiece held in the lathe spindle. To correct any axialmisalignment, various types of so-called floating tool holders have beendevised which permit the tool to float or shift laterally into alignmentwith the work.

An example of such a tool holder may be found in the patent to Miltonand Stanley Benjamin, Patent No. 2,848,239, granted Aug. 19, 1958. Thetool holder disclosed in such patent is capable of both parallel andangular floating movement with respect to its mounting means and forthat purpose there is a pin and slot connection between the tool holderand mounting means and a spring element which urges the pin into pointcontact with a second retainer pin. This particular construction hasproven to be quite satisfactory for most purposes, but there areoccasions when it is desirable to have a tool holder in which floatingmovement in a lateral direction is more precisely controlled andrequires less force, which is a principal object of this invention.

Moreover, those floating holders previously available could not be usedwith live spindles where the tool to tates and the workpiece is heldstationary, since the high friction between the relatively moving partsof the holder would severely resist the rapid back and forth movementsof the tool which would be required as it rotated.

Accordingly, it is another object of this invention to provide a fullfloating holder primarily of the rotating type.

Another object is to provide such a floating holder with novel means forpermitting such lateral shifting of the tool.

Still another object is to provide a floating holder of the typeindicated in which the angular position of the tool remains the sameduring lateral shifting thereof, whereby a simple transverse force,rather than a force couple, acting on the outer end of the tool is allthat is necessary to effect such lateral shifting.

A further object is to provide such a floating holder with novel springcentering means for yieldably maintaining the tool coaxial with theholder even when rotating at high or low speeds, whereby the amount oflat- 3,421,770 Patented Jan. 14, 1969 eral shifting of the tool requiredto bring the same into axial alignment with a workpiece is reduced to aminimum, and depends on the extent of misalignment between the holderand workpiece.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawing setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principles of the invention may beemployed.

In such annexed drawing:

FIG. 1 is a central longitudinal section of a preferred form of floatingholder constructed in accordance with the present invention;

FIG. 2 is an exploded perspective view showing the floating holder ofFIG. 1 in disassembled form;

FIG. 3 is a vertical transverse section through the holder of FIG. 1taken on the plane of the line 33 thereof; and

FIG. 4 is a partial fragmentary longitudinal section of a modified formof spring centering means for yieldably maintaining the holder housingand bushing in coaxial alignment.

Referring now in detail to the drawing and first of all to FIGS. 1 and2, a preferred form of floating holder constructed in accordance withthe present invention is indicated at 1 and generally includes acylindrical housing 2 in which there is disposed the inner end of abushing 4 having a socket 5 for receipt of a suitable collet 6 or thelike for tightly gripping the shank 7 of a rearrier 8 or similar typetool.

The collet 6 shown is of a conventional form, axially slotted fromopposite ends and having axially spaced parallel frusto-conical surfaces10 and 11 which are adapted to be moved into engagement withcorresponding frustoconical seats 12 and 13 in the bushing socket 5.Threaded onto the forward end of the bushing 4 there is a nosepiece 14having a nose ring 15 disposed therein. As apparent, when the nosepiece14 is tightened, the nose ring 15 is forced against the collet 6 tocause such collet to move inwardly against the frusto-conical seats 12and 13, causing the collet to be radially contracted into tight grippingengagement with the tool shank 7,

The bushing 4 with tool 8 carried thereby is mounted for limited lateralmovement within the cylindrical housing 2 while maintaining the angularposition of the bushing and tool coaxial with the housing through anovel connection including a driver 16 and driver plate 17, in a mannerwhich will become readily apparent in the discussion to follow. Thedriver 16 is of cylindrical form, snugly received within the housingbore 18 adjacent the back wall 19, and has a pair of diametricallyopposed, axially extending slots 20 in the outer surface thereof forkeying the driver 16 to the housing 2 by means of dowel pins 21extending through oppositely disposed openings 22 in the housing 2 andinto the slots 20.

The driver plate 17 is also cylindrical, but is loosely disposed in thehousing 2 between the driver 16 and bushing 4 due to a slight diametralclearance between the driver plate 17 and housing bore 18, and theforward face 23 of the driver 16 is centrally slotted thereacross at 24for receipt of a central projection 25 from the rear' face 26 of thedriver plate 17 so as to permit limited lateral shifting of the driverplate 17 with respect to the driver 16, but not relative rotationalmovement therebetween.

Ball bearing assemblies 29 each comprising a plurality of ball bearings30 contained in a U-shaped retainer 31 with openings 32 in the sidesthereof through which the ball bearings 30 project may be positionedbetween the adjacent surfaces 33 and 34 of the slot 24 and centralprojection 25, respectively, to reduce substantially the frictionbetween the driver 16 and driver plate 17 for ease of sliding movementtherebetween.

There is a similar connection between the driver plate 17 and bushing 4which permits transverse movement of the bushing 4 across the driverplate 17 in a direction perpendicular to that in which the driver plate17 may be moved, or substantially so. More specifically, the front face35 of the driver plate 17 has a central slot 36 thereacross similar tothe slot 24 in the driver 16-, but running in a direction perpendicularto the central projection 25 on the opposite or rear face 26, and thebushing 4 has an annular flange 37 the rear face 38 of which is cut awayto provide a central projection 39 of a size to be received within thecentral slot 36 with additional ball bearings 30 contained in aperturedretainers 31 disposed between the adjacent edges 40 and 41. As shown inFIG. 3, the ends of the retainers 31 are beveled at 42 so as not tointerfere with assembly of the driver plate 17 and bushing 4 in thehousing 2. The same is true of the retainers 31 between the driver 16and driver plate 17.

The diametral clearance between the bushing flange 37 and housing bore18 is preferably the same as between the driver plate 17 and housingbore 18, whereby the bushing 4 may be laterally shifted to the sameextent in two directions perpendicular to each other; i.e. with thedriver plate 17 in the direction of the driver slot 24, and in thedirection of the driver plate slot 36. As apparent, these perpendicularmovements will permit lateral shifting of the bushing 4 in any directionto bring the tool 8 into axial alignment with a workpiece. The diametralclearance between the driver plate 17, bushing 4 and housing bore 18should be suflicient to accommodate the maximum amount of axialmisalignment which is ordinarily encountered with a workpiece as whendrilling and reaming holes in a workpiece on a turret lathe or othermachine.

The driver 16, driver plate 17, and annular flange 37 of the bushing 4are retained within the cylindrical housing 2 by a locknut 45 which isthreaded onto the outer end of the housing 2 and may be secured in placeby a setscrew 46 or the like. The bushing 4 extends through a centralopening 47 in the locknut 45 with a sufficient clearance between thelocknut opening 47 and the adjacent bushing surface 48 so as not tointerfere with the desired lateral shifting of the bushing 4, and anO-ring 49 disposed in a groove in the locknut 45 engages the bushingsurface 48 to guard against moisture and dust particles entering theinterior of the housing 2.

Axial shifting of the various parts 16, 17 and 4 within the housing 2 isprevented by a stress washer 50 and thrust bearing 51 inserted betweenthe locknut 45 and bushing flange 37.

The floating holder 1 thus far described permits lateral shifting of thebushing 4 and tool 8 carried thereby to compensate within limits for anyaxial misalignment between the tool and a workpiece to be machinedthereby.

As an example the shank 52 of the housing 2 may be mounted in a livespindle and the tool 8 may be a reamer or other such tool. In use, ifthere is slight misalignment between the tool and a hole in a stationaryworkpiece to be reamed thereby, the ball bearing assemblies 29 willpermit substantially unrestricted shifting of the tool back and forth asthe tool and holder are rotated to compensate for misalignment. Ofcourse, the housing shank 52 may also be mounted at one of the stationsof a turret lathe for reaming holes or the like in a workpiece drilledat another of the turret stations. In actual practice, when the turrethead is indexed to bring the reamer into position for reaming the hole,there is usually a slight misalignment therebetween, whereby if the toolwere not mounted for lateral shifting movement to compensate for themisalignment, the hole would be reamed out-of-round. However, with thefloating holder 1 of the present application, the tool will shiftradially in any direction to compensate for the misalignment.

Moreover, only a simple force of small magnitude acting on the end ofthe tool is required to effect such radial movement of the tool, ratherthan a high force couple, because of the bearings 30 and the keying ofthe housing 2, driver 16, driver plate 17, and bushing 4 together asdescribed above in such a manner that the angular position of the toolis always the same; i.e., parallel to the axis of the cylindricalhousing 2.

Another important feature of the floating holder 1 not yet mentioned isthe spring centering mechanism 55 which is effective to center the toolin the housing 2 upon release of the lateral shifting force on the toolas when the tool is removed from a misaligned hole subsequent to thereaming operation while the tool is rotating at high or low speed oreven stationary. This reduces to a minimum the amount of lateralshifting of the tool required to bring it into axial alignment with anyworkpiece, and is determined by the amount of misalignment between theholder and workpiece. Moreover, with the tool ordinarily held coaxialwith the holder, such holder may be used in situations where no axialshifting is required.

Referring next to the details of the spring centering mechanism 55, suchmechanism includes a plunger 56 disposed in a counterbore 57 in thereduced end portion 58 of the bushing 4 which extends through centralapertures 59 and 60 in the drive plate 17 and driver 16, respectively,with suflicient clearance between such end portion 58 and the walls ofthe apertures 59, 60 so as not to interfere with the desired lateralshifting movement. Preferably, there is a ball sleeve 61 with aplurality of ball bearings 62 contained therein surrounding the plunger56 for permitting ready axial sliding movement of the plunger 56 withinthe counterbore 57, and there is a compression spring 63 disposed in arecess 64 in the plunger 56 for maintaining the plunger in engagementwith a ball bearing 66 located in a socket 67 in the back wall 19 of thehousing 2. The end surface of the plunger 56 which engages the ballbearing 66 has a frusto-conical depression 68 formed therein, wherebywhen a lateral or transverse force is applied to the tool to cause thetool and bushing 4 to shift laterally, the plunger 56 also moveslaterally a corresponding amount and in addition moves axially inwardlyagainst the bias of the spring 63. Later on when the lateral shiftingforce is removed from the tool, the action of the compression spring 63tending to return the plunger 56 to its original position causes theplunger and bushing 4 to be moved laterally in the reverse directionuntil the ball bearing 66 is once again properly seated within thedepression 68 and the plunger and bushing are coaxial with the housing2.

If desired, a backup screw 70 for the spring follower 71 may be threadedthrough the base 72 of the bushing 4 which when adjusted will vary theforce applied by the spring 63 against the plunger 56.

While in the preferred form shown in FIG. 1 the spring centeringmechanism 55 is carried by the bushing 4, such centering mechanism mayjust as easily be disposed in the cylindrical housing 2, as in the FIG.4 embodiment wherein the plunger 56', ball sleeve 61 with ball bearings62 therein, spring 63', and adjusting screw 70 are shown positioned inthe shank portion 52, with the ball bearing 66 located in a socket 67'in the reduced end section 75 of the bushing 4. Otherwise the structureof the FIG. 4 embodiment is the same as the FIG. 1 embodiment andaccordingly no further discussion is thought to be necessary.

From the above, it can now be seen that the device of the presentinvention is a full floating holder of a unique construction whichpermits lateral shifting of the tool carried thereby to compensate forany axial misalignment between the tool and a workpiece whether the toolbe rotating or stationary. At the same time the angular disposition ofthe tool is maintained so as to reduce to a minimum the amount of forcerequired to effect such lateral shifting. Moreover, such holder isprovided with a unique spring centering mechanism for centering the toolwithin the tool holder housing while rotating at high or low speeds orstationary upon releasing of the lateral shifting force, whereby theamount of lateral shifting of the tool required to bring the same intoaxial alignment with a workpiece is reduced to a minimum, and the holdermay be used in situations where no axial shifting is necessary.

Other modes of applying the principles of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed.

. We therefore, particularly point out and distinctly claim as ourinvention:

1. A floating holder comprising a housing having a cylindrical openingin one end, a bushing having means for tightly gripping a tool looselydisposed in said cylindrical opening, and means interconnecting saidbushing and housing for permitting limited lateral shifting of saidbushing within said housing to accommodate for axial misalignmentbetween the tool and a workpiece, said means for permitting limitedlateral shifting of said bushing as aforesaid comprising a driver platedisposed in said cylindrical opening inwardly of said bushing and havinga slight diametral clearance with the wall of said cylindrical opening,a cylindrical driver having a close fit in said cylindrical opening andkeyed to said housing inwardly of said driver plate, one of said driverplate and driver having a transverse slot therein and the other of saiddriver and driver plate having a projection extending into saidtransverse slot for permitting limited radial movement of said driverplate between diametrically opposed surfaces on the wall of saidopening, a central transverse slot in one of said bushing and driverplate, and a central projection on the other of said bushing and driverplate extending into said slot for permitting limited radial movement ofsaid bushing in a direction at an angle with respect to the direction ofmovement of said driver plate.

2. The floating holder of claim 1 further comprising bearing elementsdisposed between the adjacent surfaces of said slots and projections forpermitting ready sliding movement therebetween, said bearing elementsbeing contained in elongated U-shaped retainers with openings in theside walls through which said bearing elements project, the ends of saidretainers being beveled to provide adequate clearance with said housingto permit such radial movements of said driver plate and bushing.

3. The floating holder of claim 1 further comprising a spring centeringmeans interconnecting said housing and bushing for yieldably maintainingsaid bushing in coaxial alignment with said housing, said springcentering means comprising a plunger disposed in a recess in the innerend of said housing, said inner end of said bushing projecting throughaligned openings in said driver and driver plate, bearing elementslocated between said plunger and the wall of said recess to permit readyaxial sliding of said plunger in said recess, another bearing elementdisposed in a socket in said housing, the inner end of said plungerhaving a frusto-conical depression therein, and spring means betweensaid bushing and plunger for maintaining the surface of saidfrusto-conical depression in engagement with said another bearingelement.

4. A floating holder comprising a housing having a cylindrical openingin one end, a bushing having means for tightly gripping a tool looselydisposed in said cylindrical opening, means interconnecting said bushingand housing for permitting limited lateral shifting of said bushingwithin said housing to accommodate for axial misalignment between thetool and a workpiece, and spring centering means interconnecting saidhousing and bushing for yieldably maintaining said bushing in axialalignment with said housing, said spring centering means comprising aplunger disposed in a recess in the inner end of said bushing, bearingelements located between said plunger and the wall of said recess topermit ready axial sliding of said plunger in said recess, anotherbearing element disposed in a socket in said housing adjacent the innerend of said plunger, said inner end of said plunger having afrusto-conical depression therein, and spring means between said bushingand plunger for maintaining said inner end of said plunger in engagementwith said another bearing element.

5. A floating holder comprising a housing having a cylindrical openingin one end, a bushing having a means for tightly gripping a tool looselydisposed in said cylindrical opening, means interconnecting said bushingand housing for permitting limited lateral shifting of said bushingwithin said housing to accommodate for axial misalignment between thetool and a workpiece, and spring centering means interconnecting saidhousing and bushing for yieldably maintaining said bushing in axialalignment with said housing, said spring centering means comprising aplunger disposed in a recess in said housing, bearingelements locatedbetween said plunger and the wall of said recess to permit ready axialsliding of said plunger in said recess, another bearing element disposedin a socket in the inner end of said bushing, the outer end of saidplunger having a frusto-conical depression therein, and spring meansbetween said housing and plunger for maintaining said outer end of saidplunger in engagement with said another bearing element.

References Cited UNITED STATES PATENTS 1,027,520 5/1912 Blood 279161,377,663 5/1921 Brown et a1. 279-16 X 1,398,679 11/1921 Clark 276-161,424,535 8/1922 Watts 27916 1,818,622 8/1931 Hoeh 27916 2,460,2101/1949 Barrett 279-16 2,475,386 7/1949 Frisco 2791'6 2,826,053 3/1958Munn 279-16 X ROBERT C. RIORDON, Primary Examiner.

J. C. PETERS, Assistant Examiner.

